Our Verdict

If you need a small panel that is inexpensive, will charge your phone/tablet AND has an internal battery, this is a good deal. It performed nearly as well as is its sibling and Editors' Choice winner the Instapark Mercury 10 and yet was half the price. The Mercury 10 produces over twice the power and can charge two devices at once. The Mercury 10 is better if you don't mind a little extra weight.

After about 3 months, the 4S panel stopped working that well. It would not hold much of a charge and when plugged in, it stopped charging the iPhone short of a full charge… even in direct sun. Other user reviews have reported similar problems. For this reason, we need to test a few more of these devices before we can recommend it. In the meantime, if you are looking for a good budget and compact solar charger, we recommend going with the Anker 14W. But the 4S has the advantage of an internal battery and it can be easily clipped to your backpack while hiking. For the Mercury 10, we generally recommend getting an extra external battery, which further raises the weight and cost.

Got a laptop or larger device to charge? Read our full Portable Solar Review to see the more powerful options.

Our Analysis and Test Results

A folding solar panel with an integrated battery, the Mercury 4S is a decent panel for a fair price.

Performance Comparison

Instapark Mercury 4S

Output Power

4 W is not a mighty number but it is plenty to charge any laptop or smartphone we threw at it. At 800 mA, this panel charges a phone or tablet about as fast as any other panel we tested. Only a few other panels charged at 1000 mA or higher. In addition, the internal battery means you don't have to worry about a passing cloud interrupting the charge. This panel gives you peace of mind because you don't have to constantly monitor it to make sure it is charging.

Storage

There is no real storage with this panel. You can fold your charging cable into the panel…but it seems to always slide back out. we recommend bringing an extra soft sunglasses case to hold your charging cables.

Ease of Use

This is about the easiest panel to use if you are just charging one USB device. You just need your USB charging cord for whatever you are charging.

There are grommets at the edges of the panel for clipping to trees, tiny carabiners or string. However, the grommets are quite small so you likely need to purchase some extra string and create loops to really be able to attach the panel to much.

The panel folds into itself, which make it very compact. However, it also makes it a little hard to lay perfectly flat. Not a big deal, but something to point out as it can take a little wrestling to get the panel to face perfectly perpendicular to the sun.

Versatility

The 4S is most adept at charging smartphones or tablets. There is no CLA capability and there are no adapters. You can't even add them after the fact. You can't charge a device with no USB cable and battery chargers are also tricky. Other panels with a wider variety of adapters will be better for charging camera batteries, motorcycle batteries, laptops and a wider variety of devices.

Weight

This panel is not light, but it is light per watt. Other panels this powerful are almost twice as heavy. Another way to look at it is that this is by far the lightest panel that can charge two devices at once.

Instapark Mercury 4S on the back of a 98 Honda SuperHawk. Ride all day, charge all night.

Value

The Mercury 4S has a lock on value. Overall it is one of the least expensive panels, and it is by far the least expensive per watt. It is also by far the least expensive panel that can charge two devices at once.

Best Application

This tablet could keep one person's table and smartphone charged during heavy use. It would also work for two to four folks to keep their cellphones and tablets up and running for occasional use.

Conclusion

If you want a charger with an integrated battery and are on a budget and don't want to spring for the Poweradd Apollo 2, then this is the panel to get. Your dollar won't go any further for a small and light device that charges your tablet or phone.